Embodiments of the present invention relate to a process chamber for processing a substrate.
A process chamber is capable of processing a substrate in an energized process gas. The process chamber comprises an enclosure wall that encloses a process zone into which a process gas may be introduced, a gas energizer to energize the process gas, and an exhaust to exhaust the process gas. Typically, the enclosure wall is smooth to facilitate post-process cleaning of the enclosure wall. A process chamber may, for example, be used to deposit material on a substrate or to etch material from a substrate, for example, by sputter etching a substrate surface before a subsequent deposition process is conducted on the substrate. The sputter etching process may, for example, remove a native oxide layer from the surface of a metal layer before a metal deposition step so that the deposited metal can make good electrical contact with the underlying metal layer of the substrate.
During such sputter cleaning of the substrate, the material that is etched from the substrate can often redeposit on the substrate instead of depositing on other surfaces in the chamber. Also, material that is etched from the substrate that deposits on the enclosure wall can flake off into the process zone and fall upon and contaminate the substrate, for example, because a rise in temperature of the enclosure wall causes thermal expansion mismatch stresses which cause the deposits to flake off from the wall. In addition, outgassing of volatile material trapped in the enclosure wall can occur when the enclosure is pumped out to low vacuum pressures. These materials can further contribute to lower substrate yields.
Thus, it is desirable to have a process chamber that is capable of processing a substrate, for example by sputter etching the substrate, with reduced redeposition on or contamination of the substrate. It is also desirable to minimize outgassing from the enclosure wall of the process chamber.